Extreme cold-hardy grape developments bear fruit
The Minnesota Grape Growers Association (MGGA) has never had difficulty attracting interested growers. With the MGGA’s advocacy, the state of Minnesota began an official grape hybridization program in the mid-1980s. These efforts have resulted in the introduction of new cold-hardy grape varieties, as well as innovative cultivation techniques, and led to the expansion of vineyards into areas once thought too cold and harsh of an environment for commercial vineyards. From a mere 200 acres of grapes in 2002, to 1,500 acres under cultivation today in Minnesota alone, the success of cold climate grape research is evident.
John Thull, vineyard manager, and Jenny Bradley, vineyard staff at the University of Minnesota’s Horticultural Research Center,winter prune grape vines in February. The snow is several feet deep: the top trellis is 6 feet off the ground.
PHOTO COURTESY OF PATRICK WITHEROW
Minnesota isn’t the only state dedicating funds to cold-weather grapes. It is now estimated that over 3,000 acres of cold-climate grapes are in production across the U.S. Vineyards and wineries have sprung into existence in areas not conducive to growing traditional wine grape varieties. Over 300 wineries and 1,300 grape growers, spread across a dozen cold-climate states, are involved in the industry today, and research is occurring at institutions from North Dakota to New England. Making wine from these grape varieties has become a lucrative niche business. Growers are now seeking to push the boundaries of grape hardiness even further.
With the USDA grant, the Northern Grapes Project – as the multidisciplinary, integrative project is now known – hopes to capture the true potential of cold-climate grapes via a far-reaching collaboration of researchers, growers and winemakers alike. Region-specific research around cold-hardy grapes will help growers develop uniquely adapted viticultural procedures, while enological research will enhance the wine making capabilities of these varieties, as well as their appeal to the public.
By focusing on education and extension, the Northern Grapes Project aims to tap into the potential for farm wineries throughout cold northern climates by “supporting the people in the industry to help them make more informed decisions about what they grow and how they grow it,” as well as develop the tourism aspects of the industry, increasing the appeal of these wines, explained Tim Martinson, Northern Grapes Project director and senior extension associate at Cornell University. “We are really trying to link up the growing and the fruit characteristics with the wine making, marketing and decision making. There is vast interest from growers even in very cold environs.”
John Marshall, owner of Great River Vineyards in Lake City, Minn., has been growing grapes for 40 years.
Today, his vineyard specializes in growing and selling wine grapes to regional wineries and home winemakers, as well as offering a selection of table grapes. They also sell extremely cold-hardy grapevines wholesale and retail throughout the U.S.
“Back in the mid-1970s, when I began growing grapes, there were no wine varieties that would survive the winters here in Minnesota without being covered to keep them from freezing off,” Marshall said. However, Marshall and a small group of growers believed that northern grape growing was possible, and would prove to be a viable segment of agriculture.
“Here at Great River Vineyards, we specialize in extremely cold-hardy varieties. We feel that if a grape does not offer this level of cold hardiness, it is not reliable in our area, and in the other areas we feel benefit from our work,” Marshall said.
Cold-hardy grape breeding and research has been ongoing since the 1940s, when Elmer Swenson, a Minnesota dairy farmer, began breeding grapes using the native Vitis labrusca, or Eastern wild grape. His breeding has resulted in both table and wine grapes that can survive cold climates. Varieties of cold-hardy grapes developed at the University of Minnesota, beginning in the 1970s, have Vitis riparia, also native to North America, as a parent. Four wine grape varieties have been developed by the university, with a fifth, Frontenac blanc, now available. All are considered reliably hardy to minus 35 degrees Fahrenheit, or lower.
The grape cultivars being studied are those “whose buds survive the kinds of winter regimes that we encounter across the Upper Midwest and across the Northeastern United States, in regions that would be classified as 4a and 4b on the USDA hardiness zone map,” explained James Luby, University of Minnesota, department of horticultural science.
Low temperatures in those hardiness zones reach below minus 25 or minus 30 degrees Fahrenheit. However, it’s the grapes with the ability to withstand temperatures greater than 10 degrees colder that are pushing grape production into extreme northern areas. If the grapes don’t survive at minus 30 degrees Fahrenheit, Marshall doesn’t count it as extremely cold hardy.
“The most widely planted examples today, in the upper Midwest, are probably the four University of Minnesota cultivars Marquette, Frontenac, Frontenac gris and La Crescent; and the Swenson cultivars St. Croix and St. Pepin,” Luby said. Luby is working to develop, evaluate and ultimately introduce plant cultivars with the ability to withstand the cold climate, offer good disease and pest resistance and produce high-quality fruit.
Marshall knows that cold-hardiness depends on more than genes. “In order to get vines to survive the winter, it is important that they be properly pruned so that they do not overbear during the growing season,” Marshall noted. “Overbearing or carrying too large a crop can weaken the vine and make it susceptible to winter injury.”
Factors besides the cold temperatures also play an important role in these northern climates. Fungal disease pressure, exacerbated by the high rain and high summer humidity levels in the Upper Midwest, can impact the winter survivability of vines. Paolo Sabbatini, assistant professor of horticulture at Michigan State University, specializes in wine and juice grape cold-climate physiology.
“In Michigan and in cool regions, grape production is limited by a short growing season [140 to 160 days], and is similarly limited by low heat accumulation,” Sabbatini said. “Such environmental limitations reduce the ability of the vines to ripen fruit. In addition, vines cultivated in cool climates can begin growth late in the spring, and also experience early fall frosts, [which] can impose a premature arrest of photosynthesis, hindering fruit ripening.”
Site selection, he said, “is the single most important decision after macroclimate has been selected.” Soil, slope and surrounding environs all impact vine hardiness. “Nitrogen deficiency or excess – or that of any other nutrient – will be detrimental to vine tissue hardiness. Like nitrogen, excess water and drought is bad,” Sabbatini said.
Once site is accounted for, the survivability of cold-climate grapes isn’t just about the weather. Special treatment, year-round, is needed to retain the ability of the vine to withstand the cold. Developing techniques to increase the survivability of vines in cold climate areas is one focus of the research being done. Cultivation issues impactingvines grown in extreme weather areas are not the same as those encountered by traditional grape growers in moderate climates. Pruning, disease control, canopy management and training systems have the potential to impact the ability of the vines to survive.
“Carbohydrates are the energy which drives the metabolic machinery of the vine, and that includes cold-hardiness,” Sabbatini said. Carbohydrates are sent first to the ripening fruit. Excessive fruiting, coupled with a short period from harvest to leaf loss, means that too much fruit-bearing weakens cold-hardiness. “We must use our viticultural skills and knowledge to achieve that desired goal of balance between adequate leaf area and crop size,” he said.
In addition to close monitoring of the crop size, pruning late in the season, but still before bud break, in order to delay new growth stimulation, is important. Along with this, the retention of extra trunks, canes and buds is recommended for “vines deemed likely to suffer injury every year and damage more than once every 20 years,” Sabbatini said.
Training methods for the vines manipulate the canopy in order to facilitate light penetration. “The best choice for hardiness is one that favors photosynthesis in the renewal zone with resultant maximal darkness of cane periderm color for that cultivar,” Sabbatini said.
These practices are all labor-intensive, creating additional costs for growers, but are needed to ensure continued hardiness and good results with these grapes. Complicating things even more, the fact that practices that are beneficial in one region may not be effective in other cold-climate areas has to be addressed.
While the Midwest region is undoubtedly cold, its climate does differ from other cold-weather regions, such as the northern regions of New York State. At Cornell, Martinson’s own research will focus on whether or not “there is enough heat to consistently ripen” cold-climate wine grapes in these areas. Summer heat is not as reliable in New York as in Minnesota, and the grapes don’t always have enough time to mature during the season. Martinson will explore “ways to manipulate this through canopy and crop management, to push things in a certain direction,” he said.
Creating a market
Developing varieties that can withstand the cold, and finding the best cultivation techniques to keep them vigorous, is only a small part of the picture. These extremely cold-hardy vines are different than traditional Vitis vinifera hybrids, such as Merlot, Chardonnay and Cabernet, used to make European-style wines.
The biochemistry of these extremely cold-hardy grape varietals is not yet understood. Turning these cold-climate grapes, which typically have highly acidic berries concentrated in sugar, into a product that consumers will want to purchase is another part of the overall survivability of the industry. If no one wants these grapes, there is no point in growing them.
“Our industry in the Midwest is not a pure wine and grape industry,” Sabbatini said. “We produce small amounts of grapes and small amounts of wines that are sold mainly in the tasting room to tourists that are visiting beautiful areas such as the Great Lakes.”
Luby points to the International Cold Climate Wine Competition, held yearly, which spotlights particularly superior wines crafted from cold-climate grapes. Unlike California and European-style wines, which corner the U.S. markets, these small batch wines are unique and present a niche marketing opportunity in the ever-growing farm winery industry, attracting tourists to regionally specific products.
“It’s a tourism business,” Martinson said. While cold-climate table grapes do attract pick-your-own customers, Martinson does not foresee this becoming an industry force, leaving wine grape varieties the focus of the Northern Grapes Project. Even vineyards without wineries are ultimately selling their grapes primarily to small and midsized farm wineries that are dependent on the business of agritourism for sales.
Raising the wine bar
Katie Cook, enologist at the University of Minnesota, has been delving into the intricacies of wine making with extremely cold-hardy grape varietals. Recognizing the inherent characteristics of the fruit, she said, is the first step to success.
“While one of the objectives of using this grape [Vitis riparia] in the breeding program was to impart its super cold-hardiness into our hybrid varieties, we also inherited its tendency toward high acidity and high sugar,” Cook said. Winemakers, she explained, need to take into account these characteristics of these extremely cold-hardy hybrids and adjust their technique accordingly.
There are different types of de-acidification techniques available for highly acidic varieties. Malolactic fermentation is another option, she said, as is stopping the fermentation process with residual sugar, thus balancing the high acid content. With some varieties, particularly the Swenson cultivars hybridized from Vitis labrusca, harvest occurs when they are still a bit under-ripe, to minimize their strong “grapey” aroma, which is not considered desirable. As a result, the grapes are low in sugar, and winemakers would need to address this deficit in order to achieve the desired alcohol content.
“While making wine with hybrid grapes is really no different than making wine with classic European grapes, there are some special considerations,” she said.
Cold-climate wines take center stage at the MGGA’s annual International Cold Climate Wine Competition, held in conjunction with their annual conference. The competition, held since 2009, focuses specifically on wines made from grape varietals considered hardy, without winter protection, in USDA hardiness zone 4. Commercially produced wines, with no less than 20 cases of production, are eligible to compete. Also at this year’s MGGA Cold Climate Conference, held February 23 through 25 in St. Paul, Minn., the Northern Grapes Project researchers will introduce and discuss their objectives.
The researchers and partners involved in the Northern Grapes Project hope not only to develop new varieties, improve upon cultivation practices for cold-hardy vines, finesse wine making techniques and familiarize consumers with these fruits, but to also grow a sustainable and profitable farm economy based on super cold-hardy grape vines, reaching into areas where grape cultivation remains in its infancy, and expanding into yet more marginal areas. From vine to wine, the impact of extreme cold-hardy grapes is expected to be very fruitful, as tourism-based wine trails expand, offering quality wines from grapes grown in northern vineyards.
The author is a freelance contributor based in New Jersey. Comment or question? Visit www.farmingforumsite.com and join in the discussions.